The San Antonio, Texas, native received a trophy and a check for $50,000.
Harini went head-to-head with Vikram Raju, 12, in the spell-off, a format that tested the contestants on how many words they could correctly spell within 90 seconds.
Harini spelled 21 out of 26 words correctly, while Vikram got 15 out of 19 words right.
“I think honestly so surreal, it’s my fourth time at the Bee,” Harini said on stage holding the trophy. “This is such a dream, this is my fourth bee and I’m just so overwhelmed.”
Of the first-ever spell-off, Harini said: “At first I was a little uneasy and I decided to take it in stride … I just had to take a deep breath and tell myself to go out there and do my best and whatever happens, happens.”
The Spelling Bee, which features elementary and middle school students spelling words that would cause most adults to stumble, has had a tumultuous few years.
The preliminary rounds began Tuesday, while the quarterfinals and semifinals took place Wednesday.
This year’s host was LeVar Burton. The Emmy and Grammy-award winner hosted the semifinal and the final round of the event.
“Like a lot of folks, I look forward to the competition every year and am excited to be a part of this wonderful tradition that celebrates excellence,” he said.